Industrial controllers are specialized computer systems used for the control of industrial processes or machinery, for example, in a factory environment. Generally, an industrial controller executes a stored control program that reads inputs from a variety of sensors associated with the controlled process or machine and, sensing the conditions of the process or machine, and based on those inputs and a stored control program, calculates a set of outputs used to control actuators controlling the process or machine.
Industrial controllers differ from conventional computers in a number of ways. Physically, they are constructed to be substantially more robust against shock and damage and to better resist external contaminants and extreme environmental conditions than conventional computers. The processors and operating systems are optimized for real-time control and are programmed with languages designed to permit rapid development of control programs tailored to a constantly varying set of machine control or process control applications.
Generally, industrial controllers have a highly modular architecture, for example, that allows different numbers and types of input and output modules to be used to connect the controller to the process or machinery to be controlled. This modularity is facilitated through the use of special “control networks” suitable for highly reliable and available real-time communication. Such control networks (for example, EtherNet/IP, DeviceNet and ControlNet) differ from standard communication networks (such as Ethernet) by guaranteeing maximum communication delays by pre-scheduling the communication capacity of the network, and/or providing redundant communication capabilities for high-availability.
As part of their enhanced modularity, industrial controllers may employ I/O modules or devices dedicated to a particular type of electrical signal and function, for example, detecting input AC or DC signals or controlling output AC or DC signals. Each of these I/O modules or devices may have a connector system allowing them to be installed in different combinations in a housing or rack along with other selected I/O modules or devices to match the demands of the particular application. Multiple or individual I/O modules or devices may be located at convenient control points near the controlled process or machine to communicate with a central industrial controller via the control network.
Adapting an industrial controller to a specialized control task often requires a control program to be customized. For this reason, specialized control languages have been developed that simplify control program development including relay-ladder language (RLL) or structured block programming. These languages may incorporate graphic elements (such as contacts or functional blocks) with text labels and a simplified control-flow to facilitate troubleshooting of the program.
Emulation of industrial control devices is often desirable for logic validation of such devices prior to commissioning. Emulation typically involves replicating the behavior of one or more hardware devices in a software emulation environment executed by a host. The emulation environment is intended to mimic the actual automation hardware as closely as possible. Accordingly, an industrial control system and control program may be tested and validated in a more cost effective virtual environment prior to implementation in an actual physical environment. However, testing in a virtual environment is often configured according to the physical attributes of the host system providing the virtual environment. It is desirable to provide as much as accuracy as feasible in the virtual environment for reflecting results which might be obtained in the physical environment.